Chemotherapy, which is one of the most common cancer treatments, uses cytotoxic drugs given via peroral and parenteral administration. The major challenge with administration of conventional anticancer drugs is their non-specific distribution in the body, leading to toxicity with serious side effects. In addition, the therapeutic effect of oral drugs is limited by their low bioavailability because the drugs must pass through digestive ducts. Over the past few decades, researchers have focused on developing drug delivery systems to overcome the limitations of the conventional drug administration by improving the pharmacokinetics and biodistribution of drugs.
In recent years, green tea catechins have been studied extensively because of their health benefits, including prevention of cardiovascular diseases and cancers. Among tea catechins, (−)-epigallalocatechin-3-gallate (EGCG) is the most abundant and has been regarded to play a major role in the beneficial effects of green tea. Numerous studies have demonstrated that EGCG possesses antioxidant, antidiabetic, antibacterial, anti-inflammatory and hypocholesterolemic effects. Moreover, it has been shown to effectively inhibit tumor growth and metastasis by targeting multiple signal transduction pathways essential for cancer cell survival.
Despite these desirable activities, clinical applications of EGCG have been limited by its poor stability and low oral bioavailability. For instance, EGCG is unstable and easily decomposed under physiological environment. It was reported that EGCG had a short half-life of less than 30 minutes in 0.05 M phosphate-buffered saline (PBS) (pH 7.4) at 37° C. In addition, most of the ingested EGCG undergo extensive hydrolysis in gastric fluid, and metabolic degradation in the gastrointestinal tract. As a result, plasma concentrations of EGCG required to achieve a desired therapeutic effect cannot be reached following oral administration.
There is therefore a need to provide a drug delivery system that overcomes or at least ameliorates, one or more of the disadvantages described above. There is also need to provide a method of forming such a drug delivery system.